1. Technical Field
This invention relates generally to tubular sleeves for protecting elongate members, and more particularly to tubular sleeves having wire filaments that provide protection against at least one of electromagnetic interference, radio frequency interference, and electrostatic discharge.
2. Related Art
It is known that electromagnetic interference (EMI), radio frequency interference (RFI), and electrostatic discharge (ESD) pose a potential problem to the proper functioning of electronic components caused by interference due to inductive coupling between nearby electrical conductors and propagating electromagnetic waves. For example, electrical currents in conductors associated with an electrical power system in an automobile may induce spurious signals in various electronic components, such as an electronic module which controls the functioning of the engine. Such interference could downgrade the performance of control modules or other components in the vehicle, thereby causing the vehicle to act other than as desired.
Similarly, inductive coupling between electrical wiring and the lines carrying data in a computer network or other communication system may have a corrupting effect on the data being transmitted over the network.
The adverse effects of EMI, RFI and ESD can be effectively eliminated by proper shielding and grounding of EMI, RFI and ESD sensitive components. For example, wires carrying control signals which may be subjected to unwanted interference may be shielded by using a protective sleeve. The sleeves can be generally flat or cylindrical, wherein the sleeves are formed from electrically conductive and non-conductive constituents, with the conductive constituents typically being grounded via a drain wire interlaced with the sleeve during manufacture of the sleeve. Typically, the conductive constituents take the form of polymeric filaments, such as nylon, coated with a conductive metal, such as a silver coating. Otherwise, it is known to twist or serve individual strands of wire with standard, nonconductive monofilament and/or multifilament yarn to form a conductive “hybrid yarn.”
While RFI, EMI, and ESD sleeves constructed as described above can be generally effective at eliminating electrical interference, the sleeves can be relatively expensive in manufacture, particularly when expensive coatings, such as silver, are used, and can exhibit some inefficiency in establishing and maintaining conductive connections between the conductive fiber constituents. In addition, the conductive coating can be worn off, thereby impacting the ability of the sleeving to provide and maintain RFI, EMI, and/or ESD protection. Further, the sleeves constructed with hybrid yarns, with wire being twisted or served with standard, nonconductive monofilament and/or multifilament yarn typically exhibit end fray upon being cold cut, as the wire and standard, nonconductive monofilament and/or multifilament yarn are not fixed or otherwise bonded with one another, and thus, they are free to move relative to one another. Further, the hybrid yarns tend to shift relative to one another upon being interlaced, thereby potentially negatively impacting the ability to provide and maintain maximum shielding against EMI, RFI and/or ESD. The shifting has a negative impact as a result of the wires moving from their intended location, which tends to form enlarged openings between the wires, wherein the enlarged openings degrade the EMI, RFI, ESD shielding performance of the sleeve. Accordingly, RFI, EMI, ESD shielding which is more economical and resistant to end fray in manufacture, more efficient and less susceptible to alteration, shifting of interlaced wires or damage in use, more reliable against wear, and exhibiting an increased useful life, is desired.
A protective sleeve manufactured in accordance with the present invention overcomes or greatly minimizes at least those limitations of the prior art described above.